The present technology relates to a display unit having a light emitting element in each pixel, and an electronic apparatus having the display unit.
In a field of a display unit performing image display, there has been developed and commercialized in recent years a display unit including, as a light emitting element of a pixel, a current-drive optical element that emits light of which the luminance varies depending on an applied current value, for example, an organic electro luminescence (EL) element. Unlike a liquid crystal device, etc., the organic EL element is a self-luminous light emitting element. Hence, the display unit including the organic EL element (organic EL display unit) is not necessary to have a light source (backlight), and therefore enables weight saving, thickness reduction, and high luminance compared with a liquid crystal display unit which indispensably includes a light source. Furthermore, since the organic EL element has an extremely fast response, about several microseconds, no afterimage occurs during moving image display. The organic EL display unit is therefore expected to be the mainstream of next-generation flat panel display.
As with the liquid crystal display unit, a drive type of the organic EL display unit includes a passive matrix type and an active matrix type. The passive matrix type is simple in structure, but is difficult to achieve a large and high-definition display unit. At present, therefore, the active matrix type is actively developed. In the active matrix type, a current applied to the organic EL element disposed for each pixel is controlled by a drive transistor in a pixel circuit provided for each organic EL element.
In the active-matrix organic EL display unit, scan lines are sequentially scanned, and a signal voltage Vsig corresponding to an image signal is sampled and written into a holding capacitor in each horizontal period (1H). Specifically, write operation of the signal voltage Vsig is performed through line-sequential scan in 1H cycles. In the organic EL display unit, when a threshold voltage Vth or mobility 1H of a drive transistor varies across pixels, emission luminance of the organic EL element fluctuates, and uniformity of a screen is degraded. In the active-matrix organic EL display unit, therefore, correction operation, which reduces fluctuation of emission luminance due to variation in threshold voltage Vth or mobility μ, is performed along with the line-sequential scan in 1H cycles.
In the active-matrix organic EL display unit, since power is supplied to each pixel through a power line, a large current is applied to the power line. However, since pulse power controlling emission and extinction of the organic EL element is typically applied to the power line, a power line drive circuit has an extremely large scale, and accordingly a display panel has a large bezel storing the power line drive circuit. For example, therefore, as described in Japanese Unexamined Patent Application Publication No. 2010-160188 (JP-A-2010-160188), there is proposed a pixel circuit in which a control transistor configured to control a source voltage of a drive transistor is provided while a power line is maintained to a fixed voltage.